The present invention relates to a semiconductor device including a package board, a first DRAM that is flip-chip connected on the package board, a second DRAM that is of the same type as the first DRAM and is mounted face up on the first DRAM such that the orientation of the arrangement of the pads is at 90° from that of the first DRAM, a microcomputer chip disposed on the second DRAM, wires, and a sealing medium. The package board has a plurality of common wires for electrically connecting first electrodes for the first DRAM and second electrodes for the second DRAM. The common wires can be disposed without crossing on the surface wire layer of the package board, since the orientation of the arrangement of the pads of the second DRAM forms an angle of 90° relative to that of the first DRAM.